In the polymerization of olefins, many proposals have hitherto been made for a solid catalyst component containing magnesium, titanium, an electron donor compound and halogen as essential components and a process for the polymerization or the co-polymerization of olefins in the presence of a catalyst for polymerization of olefins comprising said solid catalyst component, an organic aluminum compound and an organic silicon compound. For example, JP-A-57-63310 and JP-A-57-63311 (The term "JP-A" as used herein means an "unexamined published Japanese patent application") propose a process for polymerizing an olefin having 3 or more carbon atoms using a catalyst comprising a solid catalyst component containing a magnesium compound, a titanium compound and an electron donor compound, an organic aluminum compound and an organic silicon compound having Si--O--C bond.
JP-A-63-92614 proposes a solid catalyst component for polymerization of olefins prepared by bringing a dialkoxymagnesium, a diester of an aromatic dicarboxylic acid, an aromatic hydrocarbon, a titanium halide and calcium chloride into contact.
On the other hand, JP-A-1-315406 proposes a catalyst for polymerizing olefins comprising a solid catalyst component prepared by contacting titanium tetrachloride with a suspension formed by diethoxymagnesium with an alkylbenzene, adding phthalic dichloride thereto to react to obtain a solid product, and further contacting the resulting solid product with titanium tetrachloride in the presence of an alkylbenzene, an organic aluminum compound and an organic silicon compound, and a process for polymerizing olefins in the presence of said catalyst.
The foregoing known techniques focus on having a high activity enough to allow the omission of a so-called deashing step, i.e., a step of removing catalyst residues such as chlorine and titanium remaining in the polymer produced as well as on enhancing the yield of stereoregular polymer or improving durability of the catalyst activity during polymerization, and achieved excellent results to these purposes. However, further improvement of rigidity of an olefin polymer is required in recent years. Therefore, the catalysts of the foregoing known techniques are not always satisfactory for the requirement.
In the slurry polymerization process which requires a solvent at the polymerization, a polymer having a low molecular solvent weight or a low stereoregularity, which is soluble in a polymerization solvent, is formed (hereinafter occasionally referred to as "polymerization solvent-soluble polymer"), especially in the polymerization of propylene, a polymer so-called "an atactic polypropylene" (hereinafter occasionally referred to as "APP") is formed. In case of increasing of the forming rate of the polymerization solvent-soluble polymer, it concerns about an undesirable effect to the operation of the process and the production cost of a polymer, because a pipeline may be blocked up during polymerization and because when the polymerization solvent-soluble polymer remains in a polymer to be a product a step for removal of the polymerization solvent-soluble polymer to cause stickiness, etc. from the polymer to be a product is required after polymerization. However, the use of the catalyst of the foregoing known techniques is not enough to solve the problems.
The objective of the present invention is to solve the foregoing problems remaining in the prior art techniques and to provide a solid catalyst component and a catalyst for polymerization of olefins, which shows a high activity and can lower the rate of forming a polymerization solvent-soluble polymer and can obtain a high stereoregular polymer in a high yield.